Large amount of information in construction projects is still stored in unstructured documents nowadays. This research focuses on the correlation mechanism between unstructured information with highly structured BIM model, realizing BIM-based retrieval of unstructured information and improving the using efficiency. Title-based and content-based automatic correlation mechanisms are provided, capable of searching correlated entities through selected document, calculating correlation index and ranking and establishing the correlation after users' confirmation. A case-study shows that if entities are well named and expressions in the document match the model, this method is able to recall all the correlated entities, ranking at the top of the list. Correlated document can also be queried dynamically based on BIM model.